Silica-gel free silica, zirconium sulfate, and sodium sulfate tanning agent



United States Patent '0 M 2,987,369 SILICA-GEL FREE SILICA, ZIRCONIUM SULFATE, AND SODIUM SULFATE TANNING AGENT Robert H. Linnell, Blawenburg, NJ. Titanium Zirconium Co., Inc., Flemington, NJ.) No Drawing. Filed June 10, 1957, Ser. No. 664,470 6 Claims. (Cl. 8-94.25)

This invention relates to novel zirconium leather tanning agents.

The present invention is a continuation in part of my co-pending application filed January 16, 1957, and having the Serial-Number 634,425, now Patent No. 2,871,- 138.

The use of zirconium chemicals as leather tanning agents has been suggested by many workers. Zirconium tanning agents have been described in the prior art as by Somerville, U.S. Patents 1,940,610 (December 19, 1933), and U.S. Patent 2,264,414 (December 2, 1941), and more recently by Paquet, U.S. Patent 2,689,163 (September 14, 1954). However the use of zirconium tanning chemicals has been very limited due to several factors. The major difiiculty in developing zirconium compounds in leather tanning has been the high cost of zirconium as compared to most other tanning chemicals. The high cost of zirconium chemicals has not been due to the zirconium ores, zircon and baddeleyite, which are plentiful and inexpensive. Difiicult and costly processing of the ores has kept zirconium in an economic position such that it has not realized its value in leather tanning.

I have now discovered relatively simple and inexpensive methods for treating zirconium ores to obtain leather tanning agents. These leather tanning agents are inexpensive and permit leather tanners to enjoy the advantages of zirconium which they have been denied in the past due to economic factors. In addition the new zirconium chemicals have certain technical advantages over zirconium materials previously known in the art.

The most readily available and inexpensive zirconium ore is zircon, a zirconium silicate. In the art most zirconium tanning agents have been water soluble salts which can be prepared only by first removing the silica from the ore. Since zircon is very inert chemically and is in fact used as a refractory, it is very difiicult and costly to remove the silica.

In an attempt to avoid the difficult silica removal step Paquet in U.S. Patent 2,689,163 (September 14, 1954), has developed zirconium tanning chemicals containing the silica as discrete silica gel particles, water insoluble, in which water soluble zirconium compounds are imbedded. Since silica gel has well-known absorbent properties a serious loss of zirconium is suffered by retention on the silica gel. Furthermore the silica gel itself serves no useful purpose in the tanning bath.

In the present invention a new leather tanning agent has been developed which is an intimate mixture of a complex zirconium sulfate-sodium sulfate and silica in a non-gel form. The actual nature of the complex zirconium sulfate is not known but the composition of this invention has less acidity than normal zirconium sulfate. The high acidity of zirconium sulfate is undesirable for many leather tanning operations as it tans too rapidly and requires excessive alkaline material for neutralization. Since the silica in this new leather tanning agent is non-gelatinous it does not absorb or occlude the zirconium. Thus my new tanning agent is more economical in that the zirconium present is substantially all available for reaction with the hides in the tanning bath. The non-gelatinous silica is substantially present as very fine particles which exerts some beneficial effect on the titles, serving as a filler.

Patented June 6, 1961 The silica in my new tanning agent also appears to enhance the tanning action of the: zirconium in some way as yet not understood. Since the silica is non-gelatinous and not slimy, on completion of the tanning action with my composition the ex cess silica may be easily washed away. The further advantage is present in that substantial quantities of sodium sulfate are released by this new tanning agent. In the present art it is common practice to either pickle the hides previous to tanning, using a salt bath such as sodium sulfate or to add the salt to the tanning bath. Since the sodium sulfate is released by my new tanning composition the extra expense and trouble of adding the salt is avoided.

The manufacture of my new tanning composition is disclosed in my co-pending application, Serial Number 634,425, filed January 16, 1957. Briefly stated the novel tanning composition is made by heating zircon ore with soda ash and then treating the thus formed sodium zirconium silicate with concentrated (66 B6. or more) sulfuric acid. It is important to use the concentrated acid as less concentrated acid will form the objectionable silica gel. The reaction is therefore carried out anhydrously by mixing the sodium zirconium silicate directly with the 66 B. sulfuric acid and obtaining in one simple step a white, free flowing reaction product suitable for direct use in leather tanning. Since the operations are simple and the raw materials soda ash, sulfuric acid and zircon ore are all inexpensive, an economically attractive zirconium leather tanning chemical is obtained.

In the tanning of leather my new zirconium tanning composition may be used in many ways. In general the new zirconium composition may be used in tanning in methods familiar to those skilled in the art. Thus it may be used as a combination tannage with chrome or aluminum, with many combinations obviously possible. It is also possible to use my new zirconium tanning agent in conjunction with formaldehyde and with many synthetic organic tanning compounds (syntans). It can therefore be seen that there is a wide usefulness for my new zirconium tanning composition.

A few examples will illustrate some of the many uses of my new zirconium tanning agent. These examples are illustrative only and are not to be construed as limiting the scope of the present invention.

Example 1 For tanning lbs. (drained weight) pickled goatskins.-The pickled goatskins (pH about 2) are drummed in a bath consisting of 20 gallons of water and 25 lbs. of the complex zirconium sulfate-sodium sulfate-silica tanning agent for 4-6 hours. The tanning liquor is then neutralized to a pH of about 4 using soda ash. The liquor is then drained and the skins washed with water and dried out. Further treatment may be carried out as desired.

Example 2 For retannage of 100 lbs. (drained weight) chrome 1eather.l00 lbs. of chrome tanned grain sides, split and shaved in the blue are drummed in 20 gallons of water and 10 lbs. of the complex zirconium sulfate-sodium sulfate-silica tanning agent are added. After drumming: 2-4 hours the skins are allowed to lay overnight in the liquor. The pH is then adjusted to about 4 with soda ash. The liquor is then drained, the skins washed well and then fat liquored. The addition of colloidal clayand titanium dioxide may be reduced from the usuai practice in the art due to the action of the fine silica from the tanning agent.

3 Example 3 For tanning of 100 lbs. (drained weight) of capeskins.100 lbs. of degreased pickled capeskins are first subjected to a formaldehyde tannage. The skins are thendtummed for 3 5 hours in abath consisting of 20 gallons of water and 15 lbs. of the complex zirconium sulfatesodium sulfate-silica tanning agent and let lay overnight. The pH is then adjusted to about 4.5 with sodium bicarbonate and the skins are washed and thoroughly drained. To. prepare a good white. leather the skins are drained and drummed 1 hour in 20 gallons of water and 15' lbs. of a good grade of sulfonated oil.

Other types of skins and. hides may be tanned with my novel zirconium tanning agent. The amount of tanning. agent, time oftanning, pre-treatmentsand other additions .will vary depending on the. type of hide, qualities desired in the final product, etc. The use of my novel zirconium tanning agent makes economically attractive theproduction of high grade white leathers, better-wear resistant and stretch resistance tannages and greater light fastness in white leathers.

It is to be understood that it is intended to cover all changes and modifications of the examples hereinchosen Y for the purpose of illustration which do not constitute departures-from the spirit and scope of the invention.

What I claim is: e

1. A' leather tanning agent in the form of a free flowing powder consisting essentially of-zirconium sulfate, sodium sulfate and finely-divided-silica, the silicabeing substantially free from silica gel.-

2. A leather tanning agent in accordance withiclaim 1- whereinthetanning agent comprises additionally a synthetic organic tanning compound.

3. A leather tanning bath consisting essentially of an aqueous composition comprising zirconium sulfate, sodium sulfate and finely-divided silica, the silica being substantially free from silica gel.

4. A leather tanning bath in accordance with claim 3 having a pH within the range from about 3.5 to about 6.5.

5. A process of tanning leather which comprises'applying to the hides to be treated a leather tanning bath consisting essentially of an aqueous tanning composition comprising zirconium sulfate, sodium sulfate and finelydivided silica, the silica being substantially free from silica gel, at a pH within the range from 3.5 to about 6.5.

6. A process in accordance with claim 5 in which the bath also includes a synthetic organic tanning compound.

References Cited in the file of this patent UNITED STATES PATENTS 2,127,304 Mauthe et al. -rAug. 16, 1938 2,264,414- Somerville ct a1. Dec. 2, 1941 2,689,163 Paquet Sept. 14, 1954 2,826,477 Rau et al. Mar. 11, 1958 FOREIGN PATENTS 913,317 France Jan. 3, 1947 OTHER REFERENCES Pacquet: Premier Congr. Intern. Union Intern. Socs. Chem. Ind. Cuir, 1949, p. 141.

Pacquet: J.I.S.L.T.C. 10, October 1951, p. 352 (Abstract of article in 1st Int. Congr. Soc. Leather Tr. Chem, 1949, 137). 

1. A LEATHER TANNING AGENT IN THE FORM OF A FREE FLOWING POWDER CONSISTING ESSENTIALLY OF ZIRCONIUM SULFATE, SODIUM SULFATE AND FINELY-DIVIDED SILICA, THE SILICA BEING SUBSTANTIALLY FREE FROM SILICA GEL. 